Impact Of Body Composition On Core Temperature Dynamics In Firefighters Under Uncompensable Heat Stress

PURPOSE: Firefighters risk heat strain and injury during occupational tasks. The present experiment sought to determine if body fat % can be used to predict the rate of core temperature acquisition throughout an exercise protocol. The exercise protocol consisted of firefighters walking on a treadmill in an environmental chamber (35 °C; 50% relative humidity) while wearing firefighter personal protective equipment (PPE). Previous research has demonstrated that body fatness impacts heat storage. Specifically, higher body fat results in impaired heat dissipation due to the low thermal conductivity of adipose tissue. No studies have determined the impact of body fatness among firefighters in full PPE. Here, we hypothesized that excess body fat would negatively impact heat dissipation among firefighters wearing PPE. METHODS: Fifteen male participants performed a steady-state exercise walking treadmill protocol in an environmental chamber (35 °C; 50% humidity) in PPE until completing the protocol, reaching a core temperature of 39 °C or a volitional maximum. Core temperature acquisition was measured as core temperature increase per minute using telemetry capsules. Body fat % was measured pre-heat stress using air plethysmography. RESULTS: Body fat % (mean ± SD = 22.4 ± 9.3%) was a predictor of the rate of core temperature increase (0.01 °C/min; p = 0.034) in the first 10 minutes of the protocol, as indicated by a linear regression analysis. Following the first 10 minutes, body fat % had no impact on core temperature acquisition. CONCLUSIONS: Higher body fat % results in delayed heat dissipation for firefighters wearing non-permeable PPE. This finding aligns with previous research demonstrating that fat's insulator properties reduce heat conduction to the periphery. Although speculative, this delay could result in thermoregulatory consequences for firefighters with excess adipose tissue. Supported by: Collaborative Intramural Research Program (CIRP) LSU Health Shreveport